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Re: [Xen-devel] [v7][PATCH 13/16] libxl: construct e820 map with RDM information for HVM guest

This approach looks like it should work, and I think given the point in
the release it would be acceptable for 4.6.

However long term I think it might make sense to try and reuse one of
the existing libxl__arch hooks, i.e.
libxl__arch_domain_init_hw_description or
libxl__arch_domain_finalise_hw_description. On ARM these are to do with
setting the Device Tree Blob, which included the memory map, so it is
somewhat morally equivalent to configuring the e820 on x86, I think.

Those hooks are only called from libxl__build_pv today, but calling them
from libxl__build_hvm seems like it would be good too.

But seems this is raising some potential risks, isn't this? Although libxl__arch_domain_init_hw_description() and libxl__arch_domain_finalise_hw_description() are NOP to x86, they're really working on ARM side. So if we call them inside libxl__build_hvm(), any affects to ARM? I'm not very sure at this point unless anyone can validate this change on ARM, or you really ensure my concerns is unnecessary.

In particular I think a call to
libxl__arch_domain_finalise_hw_description could be inserted just before
xc_hvm_build, which is similar to PV where it precedes
xc_dom_build_image, and is where you would want to setup the e820.

libxl__arch_domain_init_hw_description I think would still be a NOP on
x86, but it should probably go either just after the call to

Tiejun, would you be willing to commit to refactoring this and the
issues which Ian raised in response to #11 and #16 a subsequent clean up
series? I don't think it would even need to wait for the freeze to be
over to be posted (although it may need to wait to be applied).

Yes, I'd like to follow this once my concerns above can be eliminated.


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